uniapp怎么获取U盘文件

1. 在manifest.json文件中添加权限：

"mp-weixin": {
  "permission": {
    "scope.userLocation": {
      "desc": "获取用户地理位置"
    },
    "scope.writePhotosAlbum": {
      "desc": "保存到相册"
    },
    "scope.writeVideoAlbum": {
      "desc": "保存到视频"
    },
    "scope.record": {
      "desc": "麦克风"
    },
    "scope.camera": {
      "desc": "摄像头"
    },
    "scope.album": {
      "desc": "相册"
    },
    "scope.userInfo": {
      "desc": "用户信息"
    },
    "scope.userLocationBackground": {
      "desc": "后台定位"
    },
    "scope.address": {
      "desc": "通讯地址"
    },
    "scope.invoiceTitle": {
      "desc": "发票抬头"
    },
    "scope.invoice": {
      "desc": "获取发票"
    },
    "scope.werun": {
      "desc": "微信运动步数"
    },
    "scope.record": {
      "desc": "录音功能"
    },
    "scope.writeFiles": {
      "desc": "文件读写"
    },
    "scope.file": {
      "desc": "文件上传下载"
    }
  }
}

2. 使用wx.chooseMessageFile()方法选择文件：

wx.chooseMessageFile({
  count: 1,
  type: 'file',
  success: function (res) {
    console.log(res.tempFiles[0].path)
  }
})

其中count表示可以选择的文件数量，type表示文件类型，success回调函数中的res.tempFiles[0].path即为所选文件的路径。